1. Field of the Invention
The present invention relates to apparatus and methods which can be utilized for identifying, measuring, and monitoring metal loss through corrosion or other deleterious factors in ferromagnetic piping and ferromagnetic vessels.
2. Description of Related Art
The following patents and publications exemplify the state of the art in systems for detecting corrosion in metallic systems, particularly pipes and pipelines.
Patent Publication No. US2002/0153249 by Eric Atherton describes a metallic corrosion monitoring system which employs the measurement of electrical current flow in the metal. This method is not as sensitive as the present invention and its measurement of magnetic flux for the detection of corrosion. There are a number of similar patents which depend upon the electrical conductivity of the metal to detect corrosion. In practice, it is difficult to detect the small changes in conductivity of a metal as it corrodes, since the effects of the corrosion will generally be very small compared to the remaining metal. The present invention does not utilize the conductivity of the metal in its application.
U.S. Pat. No. 4,400,782 by Masashi Ishikawa describes a system of using a pipe as a transmission line using the conductivity of the pipe. It is not practicable for continuous monitoring of a pipeline for corrosion because the system stability of the transmission line is not sensitive to small levels of corrosion. The present invention does not utilize the conductivity of the pipe in monitoring the pipe.
U.S. Pat. No. 4,107,605 by Robert Hudgell describes a method of testing metallic pipelines using eddy current sensing coils It is not suitable for long term monitoring of pipelines for corrosion as per the present patent application, and the present invention does not use eddy currents.
Patent Publication No. US2009/0058406A1 by Mochimitsu Komori describes a method of measuring the corrosion state of a magnetic material. It utilizes a two stage method of magnetization and is distinct from the present invention which uses a continuous AC magnetization procedure.
U.S. Pat. No. 0126422 by Alfred Crouch, et. al., describes a method of measuring a surface defect in an electrically conducting material using a pair of resonant coils. It is basically an eddy current array which is substantially different from the present invention which does not use eddy current technology.
U.S. Pat. No. 7,521,917 by Katragadda et. al., describes a method of detecting material integrity which drives a current through the material and then utilizes a sensing system for the magnetic field induced in the material. It is designed for testing train rails. The present invention is specifically designed for pipelines, and is substantially different in configuration and in application.
U.S. Pat. No. 7,362,097 by Brown, et. al., describes a pipeline inspection system where the apparatus design is for the movement of flexible coils that are pushed through the interior of the pipeline. The present invention uses fixed coils on the exterior of the pipeline and does not use any movement of these coils.
Patent Publication No. US2010/0017137A1 by Legandre Emmanual describes a method of measuring the physical parameters of a pipe by comparing the magnetic permeability to the electrical conductivity using coils within a pipe. The method is substantially different from the present invention in method and in coil configurations.
U.S. Pat. No. 7,6229,116 by Gerald Meeten, et. al., describes a three coil system for measuring structural features of a bore hole casing. The system moves through the interior of the bore hole and is very different from the present invention.
U.S. Pat. No. 4,611,170 by Roderick Stanley, et. al. describes a method of inspecting ferromagnetic pipes which features three movable axially split spools of wire and saturation levels of magnetic flux in the pipe. It is moved along the pipe and utilizes differential voltages of the two end pickup coils. The system is not a monitoring system for the pipe as per the present patent description.
There are many patents for measuring metallic integrity using eddy current systems. The present invention is not an eddy current system, and does not use eddy current technology. Also, the present invention utilizes computer(s), and digital processor(s) in order to provide a stable method of monitoring and correcting for the variable factors which affect the detection of corrosion and deterioration of pipelines and vessels.